1. Field of the Invention
The invention relates to a biocompatible polymer and in particular to a biocompatible polymer for covalently modifying magnetic nanoparticles.
2. Description of the Related Art
Magnetic resonance imaging (MRI) is an appealing noninvasive approach for early cancer diagnostics and therapeutics. MRI utilizes radio frequency pulses and magnetic field gradients applied to a subject in a strong field to produce images. MRI is capable of showing several different characteristics of tissues. The level of tissue magnetization at specific signal recording periods during the MR imaging cycle generally determines the brightness of a particular tissue in the MRI images. Contrast is produced when tissues do not have the same level of magnetization.
While the imaging capabilities of MRIs have revolutionized imaging technology, the resolution is limited to the elucidations of lesions within the body on the order of 1 mm. This limitation has led to the development of contrast enhancement agents. Because of the superparamagnetic property, iron oxide nanoparticles have been found effective as contrast enhancement agents for MRIs. The magnetic nanoparticle can be modified with a biocompatible polymer to prolong the particle circulation time in blood and reduce immunogenicity. Furthermore, the magnetic nanoparticle can be modified with a fluorescent dye and a specific targeting agent to provide fluorescent properties and specific targeting functions.
U.S. Patent Publication No. 20070148095 discloses a multi-modality contrast agent with specificity for both magnetic and optical imaging. The multi-modality contrast agent includes a magnetic nanoparticle, a biocompatible polymer chemically modifying the magnetic nanoparticle, a fluorescent dye coupled to the biocompatible polymer, and a specific targeting agent coupled to the biocompatible polymer. The biocompatible polymers include polyethylene glycol (PEG), polylactic acid (PLA), PLA-PEG, poly(glycolic acid) (PGA), poly(ε-caprolactone) (PCL), poly(methyl methacrylate) (PMMA), and the like.
U.S. Patent Publication No. 20070148095 discloses a silane compound for modifying magnetic nanoparticle and a method for using the nanoparticle to detect and treat tissues of interest.
Commercially available MRI contrast enhancement agents include Feridex® (dextran-coated iron oxide) and Resovist® (carboxydextran-coated iron oxide).